Process for molding of hollow articles

ABSTRACT

Disclosed is a process for the molding of hollow articles such as full length Foley catheters. The apparatus preferably comprises a mold with two lumen forming wires longitudinally disposed therein. A set of two receiving wires are spaced distally from the distal ends of the lumen forming wires and are longitudinally aligned therewith. A first follower is slidably disposed about the lumen forming wires in close abutment with the wires and inside wall of the mold. The first follower is preferably disposed toward the proximal end of the mold and preferably at least two other followers are provided spaced distally of the first follower. One of the other followers preferably bridges the space between the lumen forming wires and receiving wires. Sets of gates are preferably provided along the length of the mold in fluid communication with a source of molding material. In practice, molding material is injected into the molding channel at the proximal end of the mold and flows longidutinally toward the distal end of the mold while pushing the first follower along the wire ahead of it. As the follower proceeds toward the distal end of the mold, it engages and pushes the remaining followers toward the distal end of the mold. At the beginning of the molding process, each set of gates has a follower that is transversely aligned with it so as to seal the set of gates and prevent the flow of molding material through the set of gates and into the mold. In this fashion, molding material is not introduced through a set of gates and into the mold until all followers are distally located from the set of gates.

BACKGROUND OF THE INVENTION

This invention relates to a molding process for producing hollowarticles, particularly full length Foley catheters. In the past, hollowarticles have been produced by a variety of dipping, molding andextrusion apparatus and processes. However, each of these prior artprocesses and apparatus have suffered from disadvantages that aresubstantially overcome by the present apparatus and process.

In the dipping processes known in the prior art, a wire is dipped into aliquified material to be formed into the hollow article. With each dipof the wire more product from the bath adheres to the coated wire untileventually the desired amount of material is built up onto the wire.Then the material coated on the wire is sufficiently hardened so as topermit the hollow article surrounding the wire to be peeled or strippedtherefrom. One disadvantage of the dipping process is the large numberof dips and great amount of time sometimes required to build up thedesired amount of material on the wire. Additionally, when the hollowarticle to be manufactured requires small diameter wires, many materialsare too viscous in a liquified state for the wire to be dipped thereinwithout bending of the wire.

As with the above described prior art dipping processes, other prior artprocesses also have disadvantages. For instance, extrusion processes arenot advantageously employed to obtain products with a closed end.Further, while many molding processes may be employed to obtain productswith closed ends, these processes are generally not advantageouslyemployed when the article is relatively long and slender. The reason forthis is that the portion of the mold defining the hollow portion of thefinal product is often unstable and bends at the high pressures employedin the molding process.

The above noted deficiencies in prior art processes and apparatus aresubstantially overcome by the process and apparatus disclosed in U.S.Pat. application Ser. No. 580,881, filed May 27, 1975. The apparatus ofthe above-noted application comprises a mold cavity with a first wirelongitudinally disposed therein. A second wire may be spaced distallyfrom the distal end of the first wire in longitudinal alignmenttherewith. Upon injection of molding material into the mold, saidmaterial flows longitudinally toward the distal end of the mold cavitypushing the follower ahead of it. When the follower reaches the distalend of the first wire, it continues to move distally in the mold ontothe second wire thereby bridging the gap between the first wire and thesecond wire. Eventually, the follower disengages entirely from the firstwire to provide a hollow article with a solid tip. If a hollow articlewithout a solid tip is desired, only one wire is used and the followerdoes not disengage from the wire.

The process described in the above-noted application has twodisadvantages. First, it is difficult to produce long articles withrelatively small hollow portions according to the process and apparatusdisclosed because the small wire required is distorted by the highpressures required. For example, full length Foley catheters can not beproduced by the process and apparatus disclosed in U.S. application Ser.No. 580,881 because the small inflation lumen wire is distorted by thehigh process pressures required to such an extent that the wire touchesthe mold wall to provide a useless inflation lumen with a hole in it.Second, when a hollow article with a solid tip is produced according tothe process and apparatus of the above-noted application, the followeris transferred from a first wire to a second wire. However, the firstwire may be twisted with respect to the second wire by the highpressures required, thereby preventing the smooth transfer of thefollower from the first wire to the second wire. As described in U.S.application Ser. No. 580,881, the seriousness of this problem may bediminished by using specially designed followers and second wires inwhich the cross sectional area defined by the inside wall of the distalend of the follower is larger than the cross sectional area defined bythe proximal end of the second wire. However, the specially designedfollower and second wire of the above-noted application may not alwaysaccomplish their intended function, and at any rate, an apparatus andprocess that do not require a specially designed follower and secondwire would be most desirable.

The process of the present invention may be used to produce hollowarticles from a wide variety of materials, including materials which aretoo viscous in a liquid state to be used to produce hollow articles byprior art dipping processes. Additionally, the process and apparatus ofthe present invention may be employed to produce hollow products withone of the ends closed by a solid tip. Further, the process andapparatus of the present invention may be used to produce long articleswith relatively small, long hollow portions, such as Foley catheters.Finally, the process of the present invention may be used to producehollow articles with a solid tip without requiring the use of aspecially designed follower and second wire.

SUMMARY OF THE INVENTION

The apparatus of one embodiment of the present invention comprises amold with at least a first wire longitudinally disposed therein. Firstand second followers are slidably disposed about the first wire in closeabutment with both the wire and inside wall of the mold. A set of gatesin fluid communication with a source of molding material is provided inthe walls of the mold. At the beginning of the molding process, thesecond follower is spaced distally of the first follower and ispositioned to seal the set of gates. Molding material is then introducedthrough a gate into the annular space defined by the wire and inside ofthe mold proximally of the proximal end of the first follower. Themolding material thus introduced into the annular space flowslongitudinally toward the distal end of the mold while pushing the firstfollower along the wire ahead of it. As the follower proceeds toward thedistal end of the mold, the first follower reaches the second followerand pushes it toward the distal end of the mold. As the first followerproceeds to push the second follower distally, the followers willeventually no longer seal the set of gates. At such time, moldingmaterial will flow into the annular space through the gates therebypushing the followers toward the distal end of the mold. It will beappreciated by those skilled in the art that process pressures arereduced by providing multiple inlets into the mold as described above.The lower process pressures required, in turn, reduce distortion of thewire in the mold.

In a second embodiment of the invention, a hollow article with a solidtip may be produced. In the second embodiment, there is provided asecond wire spaced distally from the distal end of a first wire andlongitudinally aligned therewith. A first follower is slidably disposedabout the first wire in close abutment with the first wire and inside ofthe mold. A second follower is provided which bridges the gap betweenthe first wire and second wire. Molding material is then injectedthrough a gate into the annular space defined by the first wire and themold and flows longitudinally toward the distal end of the mold whilepushing the first follower ahead of it. As the follower proceeds alongthe wire toward the distal end of the mold, the first follower reachesthe second follower and proceeds to push the second follower toward thedistal end of the mold. Eventually, the first follower disengages fromthe first wire and entirely engages with the second wire. Because thefirst follower is substantially aligned with the second follower whenthey first touch, the transfer from the first wire to the second wiremay frequently be smooth. However, the transition from the first wire tothe second wire may be facilitated by notching the first follower andsecond follower so that they will not twist with respect to each otheronce they are engaged.

It is within the scope of the present invention to employ both afollower which initially seals gates and a follower which bridges wiresin the same apparatus. Additionally, multiple wires may be employed toprovide articles with multiple hollow portions therein. The above notedfeatures are concurrently used in the most preferred embodiment of thepresent invention to produce a full length Foley catheter.

To produce a full length Foley catheter, there is provided a mold withdrainage lumen and inflation lumen wires longitudinally disposedtherein. Two receiving wires are spaced distally from the distal ends ofthe drainage lumen and inflation lumen wires and are longitudinallyaligned therewith.

Preferably three followers are slidably disposed about the drainagelumen and inflation lumen wires in close abutment with the wires andinside wall of the mold, and a fourth follower is positioned so that itbridges the space between the lumen wires and receiving wires. The fourfollowers are preferably about evenly spaced between widened funnelforming portions of the lumen wires and the end of the lumen wires. Thefirst three followers located along the longitudinal axis of the moldare initially transversely aligned with three sets of opposing gates. Asnoted supra, the fourth follower bridges the space between the lumenwires and the receiving wires.

In operation, molding material is introduced into the mold through agate proximally of the first follower. The molding material then flowstoward the distal end of the mold pushing the first follower ahead ofit. As the follower is pushed distally, the first set of gates which wasinitially sealed by the first follower is opened and molding materialflows into the molding channel through these gates.

The first follower continues toward the distal end of the mold inresponse to the pressure of molding material injected through the firstset of gates until the first follower meets and engages with a secondfollower. The two followers then continue together distally in the molduntil the second set of gates is no longer sealed. Thereafter, moldingmaterial flows into the molding channel through the second set of gates.

We have found that if at least two sets of gates are not employed whenproducing a full length Foley catheter, the inflation lumen wire isdistorted by the forces in the mold until it touches the wall of themold. This, of course, results in a useless inflation lumen with holesin it.

Moreover, to insure wire stability, it is preferred that a thirdfollower and a third set of gates be used in the mold. Initially thethird follower is aligned with and seals a third set of gates in thesame fashion described above in connection with the first two followers.After the first three followers have proceeded in the mold cavity pastthe third set of gates, eventually, the distal end of the third followerreaches and engages the proximal end of the fourth follower. Unlike theprevious three followers, the fourth follower is not transverselyaligned with a set of gates but, rather, bridges the space between thedrainage lumen and inflation lumen wires and the receiving wires. Inthis fashion it is insured that the lumen forming wires are aligned withthe receiving wires at the time the proximal end of the fourth followerdisengages from the lumen forming wires.

To insure that the lumen forming wires and the followers remain alignedwith the receiving wires as the followers proceed through the spacebetween the lumen wires and receiving wires, the followers may beinterlockingly notched so that they will not twist with respect to eachother. Thus, if the lumen wires or any follower is twisted slightly inresponse to process pressures, then all the followers and the proximalends of the receiving wires are twisted in the same fashion to insurethat the followers remain aligned with the receiving wires.

As the followers continue to proceed distally in the mold, eventuallythe first follower disengages totally from the drainage lumen andinflation lumen wires and continues distally until finally it is totallyengaged with the receiving wires. In this fashion, molding material ispermitted to flow inwardly across the entire cross section of the moldbetween the distal end of the drainage lumen and inflation lumen wiresand the proximal ends of the receiving wires thereby forming the solidtip of the Foley catheter. Desirably, the proximal ends of the firstfollower and the receiving wires are concave so as to provide a rounded,smooth tip.

During the molding process the mold is preferably maintained at asuitable temperature so that shortly after the followers reach thedistal end of the mold the molding material will be cured or hardened.After the molded material is sufficiently cured or hardened, the mold isopened and the hollow article is stripped or peeled from the lumenforming wires. Molding material will also have hardened in the gates andinputs thereto in the mold. This material may be easily removed from thecatheter by a cutting operation either before or after the catheter ispeeled from the lumen forming wires. Thereafter, holes are provided inthe catheter in communication with the drainage and inflation lumens byconventional techniques. Finally, a balloon is attached near the distalend of the catheter to obtain the completed Foley catheter.

The number of followers used in the present invention may be increasedindefinitely until a substantial portion of the mold is filled withfollowers, in which case it is preferred to use a single continuousfollower. The single continuous follower functions substantially in thesame manner as the followers described above, except that it maysimultaneously block more than one set of gates and bridge the spacebetween lumen wires and receiving wires.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the mold employed in one embodiment of the presentinvention.

FIG. 1A shows a cross section of FIG. 1 along line 1-A--1-A.

FIG. 2 shows the mold employed in another embodiment of the invention.

FIG. 3 shows three notched followers about to engage one another used inthe preferred embodiments of the present invention.

FIG. 4 shows the mold used to manufacture Foley catheters according to apreferred embodiment of the present invention.

FIG. 4A shows a cross-section of FIG. 4 along lines 4A--4A.

FIG. 5 shows another embodiment of the present invention.

FIG. 6 shows the orientation of wires and followers at one time duringthe process using the apparatus shown in FIG. 2.

FIG. 7 shows two notched followers about to engage one another.

FIG. 8 shows the mold used in another embodiment of the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, there is shown in cross section mold 10 with wire11 and followers 12 and 13 provided therein. As shown in FIG. 1, wire 11is hung from a source 17 and terminates at 18 close to the distal end 14of mold 10. However, it is to be understood that any suitable means forproviding the wire in the mold may be used in the invention. Forinstance, the wire 11 may be imbedded into or adhesively attached to thedistal end 14 of mold 10.

As shown in FIG. 1, followers 12 and 13 fit snugly into the annularspace 15 in close abutment with wires 11 and the inside wall of mold 10.As described more fully in U.S. application Ser. No. 580,881, thefollowers 12 and 13 fit into the mold 10 so that in use the followerswill not move prematurely or permit the flow of material into the spacesbetween the followers 12 and 13 and the inside wall of mold 10 or wire11.

At the start of the process, molding material is injected from a source(not shown) through line 16 to two runners 19 and 20 that extend alongopposed sides of the mold. Runners 19 and 20 are preferably identicallydesigned and symmetrically oriented with respect to the mold 10 so thatin use, the flow of molding material will be substantially the same ineach runner. As molding material proceeds to flow along the runners 19and 20, eventually some of the molding material will flow via lines 21and 22 through gates 23 and 24 into annular space 15 proximally offollower 12.

While opposed gates 23 and 24 are used to introduce molding materialproximally of first follower 12 in the embodiment shown in FIG. 1 (andin other embodiments described below), it is to be understood that asingle gate may be used to introduce molding material proximally offollower 12. It is further to be understood that the source of moldingmaterial for each gate 23 and 24 (and for the other gates used in thisembodiment and other embodiments described below) need not be the sameas shown in FIG. 1.

The molding material injected into the mold 10 flows through annularspace 15 pushing follower 12 ahead of it until the distal end offollower 12 reaches the proximal end of follower 13. In the meantimerunners 19 and 20, as well as lines 124 and 125 and gates 26 and 27,have been filled with molding material. Injection of molding materialinto the mold via gates 26 and 27 is prevented up to this point however,because follower 13 is initially positioned in the mold 10, as shown inFIG. 1, to seal gates 26 and 27. However, when follower 12 reachesfollower 13, it continues along the mold pushing follower 13 ahead of ituntil eventually gates 26 and 27 are unsealed when the proximal end offollower 12 passes gates 26 and 27. At this time, molding material isinjected into mold 10 via gates 26 and 27 and flows through annularspace 15, pushing followers 12 and 13 toward the distal end 14 of mold10.

In the embodiment shown in FIG. 1 and 1A (and in other embodimentsdescribed below) runners 19 and 20, lines 21, 22, 124 and 125, and gates23, 24, 26 and 27 are preferably identically designed and symmetricallyoriented with respect to mold 10. The reason for this is that when asmall wire is used in the invention, it is important the the wire is notsubjected to any pressure that might distort it. Therefore, gates 26 and27 oppositely oppose each other at the same longitudinal distance alongthe mold as shown in FIGS. 1 and 1A so that opposing forces frommaterial injected through the gates 26 and 27 tend to cancel each otherout. It will be appreciated that when a small wire is used in theinvention more than two gates may be suitably arranged symmetricallyaround the periphery of the mold within the scope of the presentinvention. Further, it will be appreciated that a ring gate envelopingthe entire mold may be used pursuant to the present invention. Finally,it will be appreciated that in some circumstances, e.g., where thickwires are used, single gates may be used instead of sets of gates alongthe length of the mold. A single gate may also be used when it isdesired to introduce molding material through the proximal end wall ofthe mold.

It should be recognized that the relative dimensions of the componentparts of the mold assembly shown in FIG. 1 (as well as in FIGS. 2 and 4to 6) are distorted for the purposes of illustration. In practice it iscontemplated that the cross sectional area of runners 19 and 20 will besubstantially larger than the cross sectional area of annular space 15.Thereby, the pressure drops that occur in the runners will besubstantially lower than the pressure drops that occur in the molditself with the result being that substantially lower pressures can beemployed in molds that employ multiple sets of gates. The reduction ofprocess pressures permitted by the apparatus and process of the presentinvention is particularly advantageous when small wires (e.g., 0.035inch diameter), which can be easily distorted, are used.

It will be appreciated by those skilled in the art that the manner inwhich the gates are sealed by a movable follower is characterized by itsrelative simplicity. Other methods and means of sealing the gates, e.g.,by valves actuated by pressure transducers, could be used, but theseother methods and means would be much more complicated and costly thanthe method and means used in the present invention.

As was noted supra, the gates used in the present invention arepreferably identically designed so that the forces exerted by moldingmaterial injected into the mold via the opposing gates tend to balanceeach other. The preferred dimensions of the gate used, of course, willvary depending on the particular process and apparatus parametersemployed, e.g., width of wires, length of the mold, molding material,etc. However, when producing Foley catheters, as described in moredetail below, the gates are preferably 0.100 inch long and have a crosssectional area of 0.050 inch by 0.100 inch.

Preferably, each follower used in the present invention is provided withat least one air vent and most preferably two air vents 28 and 29, asshown in FIG. 1A. The purpose of these air vents is to relieve airpressure caused by the compression of the air space in the mold duringthe molding process. At least one air vent (not shown) is also locatedat the distal end of the mold. The design of the air vents is notparticularly critical, but the vents 28 and 29 should preferably be outof alignment with gates 26 and 27, as shown in FIG. 1A, and should besmall enough to prevent the passage of substantial amounts of moldingmaterial into the space defined by the vents 28 and 29 and the insidewall of the mold 10.

As is apparent from FIG. 1, when followers 12 and 13 reach the distalend of mold 10, follower 12 is still on wire 11. As a result, a hollowarticle with an open end is produced. However, it is to be understoodthat the mold may be designed so that both followers 12 and 13 disengageentirely from wire 11 to provide a hollow article with a pigtailed tip.As described in U.S. application Ser. No. 580,881, the pigtail on thetip results from molding material flowing into the holes provided infollowers 12 and 13.

After follower 13 reaches the distal end of mold 10, the moldingmaterial is hardened by known processes. Thereafter, the mold is openedand the hollow article is stripped from the wire. When the moldingmaterial is catalyzed silicone rubber, it is desirable to heat the moldas described in U.S. application Ser. No. 580,881 to partially cure themolding material during the molding process.

Referring now to FIG. 2, there is shown an apparatus for producing aclosed ended hollow article according to the present invention. Morespecifically, and for purposes of illustration, there is shown anapparatus for producing a nonretention urinary catheter.

Urinary catheters, as is well known to physicians, are used in thetreatment of individuals who have lost control of their urinaryfunction. One generally accepted medical practice involves inserting atube or catheter into the urinary passage until the remote or distal endis located within the bladder. The near or proximal end of the catheterremains outside the body. Often the most proximal end of the catheter isin the shape of a funnel. The funnel is in communication with a path ordrainage lumen that is provided along the longitudinal axis of thecatheter. The distal end of the catheter contains a hole incommunication with the drainage lumen such that in use the bladder maydrain through the hole into the drainage lumen and out through thefunnel into a suitable receptacle. While the invention is described withrespect to urinary catheters, it is to be understood that other types ofcatheters, e.g., tracheal catheters, venous catheters, etc. operate onsimilar principles and may be manufactured according to the presentinvention.

As shown in FIG. 2, there is provided mold 30 with first wire 31longitudinally disposed therein. A second wire 34 is also provided andis longitudinally aligned with the first wire. Wire 31 is attached to asuitable source which, as shown in FIG. 2, may be the proximal end ofmold 30. As shown, the distal end of the first wire 31 is spaced fromthe proximal end of the second wire. The proximal end of the first wire31 is preferably widened so that a catheter with a funnel at itsproximal end is provided by the process of the present invention.

At the beginning of the molding process, a first follower 32 ispreferably positioned a short distance from the widened portion of wire31. A second follower 33 is positioned so that it bridges the spacebetween the distal end of the first wire 31 and the proximal end of thesecond wire 34, as shown in FIG. 2. The followers 32 and 33 are againfitted snugly into annular space 36 closely abutting wires 31 and 34 andthe inside of mold 30 as described above in connection with FIG. 1.

With the followers so positioned, molding material, e.g., catalyzedsilicone rubber, is introduced into the mold from a source not shown vialine 37, runners 38 and 39, lines 40 and 41 and gates 42 and 43. Again,for reasons discussed above in connection with FIG. 1, it is preferredthat the runners, lines and gates are identically designed andsymmetrically oriented with respect to mold 30, although such design andorientation is not essential when employing the relatively thick wires(about 0.150 inch diameter) used to form the drainage lumens ofnonretention urinary catheters.

The catalyzed silicone rubber which has been injected into the mold viagates 42 and 43 flows through annular space 36 and pushes follower 32ahead of it. Eventually, the distal end of follower 32 reaches theproximal end of follower 33. At this point, the follower 32 continues toslide along wire 31 in response to the pressure of injected siliconerubber pushing follower 33 ahead of it. Eventually, both the firstfollower 32 and second follower 33 are entirely disengaged from thefirst wire 31 so that molding material may spread throughout the crosssection defined by the inner wall of mold 30 thereby providing a solidtip for the catheter. When the distal end of the second follower 33reaches the distal end of mold 30, the movement of the two followersstops. At this point, desirably the rounded proximal edges of firstfollower 32 are aligned with rounded proximal end of second wire 34 asshown in FIG. 5 of U.S. application Ser. No. 580,881 to provide acontinuous smooth tip for the catheter. To complete the molding process,the molding material is hardened, the mold is opened and the catheter isstripped or peeled from the wire 31 as described above in connectionwith the description of FIG. 1. Thereafter, at least one drainage holeis provided toward the distal end of the catheter in communication withthe drainage lumen.

It will be appreciated by those skilled in the art that the proportionsshown in FIG. 2 are not the proportions which would be employed normallyin the manufacture of urinary catheters. That is, a typical urinarycatheter may be about 16 inches long and about 0.24 inches in diameter.

The catalyzed silicone rubber composition used in this embodiment of theinvention (as well as the other embodiments described herein) may beprepared in the same manner and from the same materials as described inUnited States application Ser. No. 580,881. Additionally, the siliconerubber is suitably injected at the same temperatures and pressuresdescribed in the above-noted application. Even further, the materialsused for the wires and followers in all embodiments of the presentinvention are preferably the same as the materials used in theabove-noted application.

In the above-noted application, a second follower 33 was not used tobridge the space between first wire 31 and second wire 34. Rather, aspecially designed first follower was used to insure a smooth transitionof the first follower 32 from the first wire 31 to the second wire 34.In the present invention, however, second follower 33 stabilizes thefirst wire 31 with respect to the second wire 34 thereby helping toinsure the smooth transition of the first follower 32 from the firstwire 31 to the second wire 34. As a result, specially designedfollowers, such as those described in the above-noted application, arenot required in the present invention.

It will be appreciated by those skilled in the art that the embodimentsshown in FIGS. 1 and 2 may be combined to give a process and apparatuswith three or more followers. It will further be appreciated by thoseskilled in the art that when the wires and followers are oriented asshown in FIG. 6, the hole in the first follower 32 will belongitudinally aligned with second wire 34. That is, as long as thedistal end of the first follower 32 is aligned with the distal end ofwire 31, the first follower 32 will still be aligned with second wire34. However, particularly when the wires are not concentric with theinner wall of the mold (as described infra in connection with FIG. 5),as the followers proceed distally in the mold beyond the orientationshown in FIG. 6, second follower 33 will no longer be engaged with thefirst wire 31 and therefore will be free to twist with respect to thedistal end of first wire 31. As a result, the distal end of first wire31 may no longer remain longitudinally aligned with the proximal end ofsecond wire 34.

Thus, in the embodiment shown in FIG. 2, first follower 32 may becomemisaligned with the second wire 34 thereby preventing the smoothtransition of the first follower 32 onto the second wire 34. Themisalignment problem noted above may be overcome, however, by notchingthe followers used in the present invention so that they will interlockwith each other thereby preventing the twisting of one follower withrespect to another follower. One manner of interlockingly notching thefollowers is shown in FIG. 3.

Referring to FIG. 3, there is shown first follower 90, second follower91 and third follower 92 arranged in the same order as they would beprovided in a mold containing three followers. The followers areprovided with holes 93, 94 and 95 represented by the dotted lines. Itwill be observed that the distal end of follower 90 and the proximal endof follower 91 are notched so that the followers 90 and 91 willengagedly interlock so that they can not twist with respect to eachother. The distal end of follower 91 and the proximal end of follower 92are similarly notched. In this fashion it is assured that once thefollowers are engaged with one another, they will not twist with respectto each other. This, in turn, insures the smooth transition of followers90 and 91 onto the second wire.

The smooth transition of followers 90 and 91 onto the second wire may befurther insured by tapering outwardly the distal ends of holes 93 and 94as shown in FIG. 3. By so tapering the holes 93 and 94, the crosssectional areas defined by the inner walls of the distal ends offollowers 90 and 91 are larger than the cross sectional area defined bythe proximal end of the second wire. It is to be understood, however,that followers with tapered holes as described above are not part of thepresent invention per se but rather are part of the invention describedin U.S. application Ser. No. 580,881. It is further to be understoodthat the taper in the inside walls of the followers used in the presentinvention need not be as great as the taper used in the above-notedapplication. The reason for this is that the use of notched followers,one of which initially bridges the first wire and second wire, largelydiminishes or eliminates the need for specially designed inside walls inthe followers used in the present invention.

Before the notched followers 90-92 engage one another in the mold theymay be twisted and turned with respect to each other due to forces inthe mold. Referring now to FIG. 7, there is shown two followers 80 and81 that are engagedly notched with respect to one another. However, itwill be appreciated by those skilled in the art that if followers 80 and81 are twisted with respect to each other in the mold they will notengage each other since the notches walls 82 and 83 of the followers areparallel to the longitudinal axis of the mold. It is therefore preferredin the present invention to angle the notched walls 96-99 of followers90-92 with respect to the longitudinal axis of the mold as shown in FIG.3. In this fashion the followers 90-92 will initially engage with oneanother even if the followers are twisted with respect to each other andself align as the engagement is completed.

As was noted supra in connection with the description of FIG. 2,non-retention urinary catheters may be produced according to oneembodiment of the invention. However, one disadvantage of non-retentionurinary catheters is that the patient using the catheter must remainessentially immobile while the non-retention catheter is inserted inhim. Thus, generally, the catheter must be inserted into and removedfrom the patient each time the bladder is drained. As a result, it isgenerally preferred to use retention or Foley catheters which mayconveniently remain in the patient for extended periods of time.Typically, retention is provided by including an inflatable balloon nearthe distal end of the catheter. During insertion, the balloon isdeflated. After the distal end of the catheter is positioned within thebladder, the balloon is inflated by passing a fluid, typically water,through a passage within the catheter called an inflation lumen. Whenthe balloon is inflated, the inflation lumen is sealed and the inflatedballoon within the bladder insures retention. Thereafter the bladderdrains through the drainage lumen provided in the catheter and runningparallel to the inflation lumen.

Referring now to FIG. 4, there is shown an apparatus for producing aFoley catheter. More specifically, there is shown mold 50 with drainagelumen wire 51 and inflation lumen wire 52 provided therein. Spaceddistally from the drainage lumen wire 51 and inflation lumen wire 52 andlongitudinally aligned therewith are first receiving wire 53 and secondreceiving wire 54. Toward the proximal end of mold 50 the mold forks andthe drainage lumen wire 51 and inflation lumen wire 52 widen so that theproximal end of the Foley catheter is provided with separate funnels incommunication with the drainage and inflation lumens.

At the beginning of the molding process, a first follower 55 ispositioned in molding channel 155 a short distance from the funnelportions of drainage lumen wire 51 and inflation lumen wire 52. At thebeginning of the molding process, second and third followers 56 and 57are positioned distally of the first follower, preferably at evenlyspaced intervals along the length of the drainage lumen and inflationlumen wires 51 and 52. A fourth follower 58 is initially positioned tobridge the gap between the lumen wires 51 and 52 and first and secondreceiving wires 53 and 54. All followers are again fitted snugly intomolding channel 155 closely abutting the lumen wires and receiving wiresand the inside of mold 50 as described above in connection with FIGS. 1and 2. Again, for purposes of illustration, the proportions shown inFIG. 4 are not the proportions which normally would be employed in themanufacture of Foley catheters.

To begin the molding process, material to be molded, e.g., catalyzedsilicone rubber, is introduced into the proximal end of mold 50 from asource not shown via line 59, runners 60 and 61, lines 62 and 63 andgates 64 and 65. Only one gate is required for each wire in the twofunnel forming sections at the proximal end of mold 50 since the wiresat these locations are relatively stable and are not substantiallydisplaced by injecting molding material through a single gate.

Runners 60 and 61 continue past lines 62 and 63 and are in fluidcommunication with lines 66 and 71, which in turn are in fluidcommunication with gates 72 and 77, respectively. At the beginning ofthe molding process, the followers are arranged with respect to gates 72to 77 as shown in FIG. 4, i.e., follower 55 seals gates 72 and 73,follower 56 seals gates 74 and 75, and follower 57 seals gates 76 and77.

As in the embodiments shown in FIGS. 1 and 2, the runners, lines andgates are preferably identically designed and symmetrically arrangedwith respect to the mold 50. The process and apparatus illustrated inFIG. 4 also works in substantially the same fashion as the embodimentsshown in FIGS. 1 and 2. That is, the molding material introduced viagates 64 and 65 travels distally in the mold eventually reachingfollower 55. Thereafter, molding material continues to travel distallyin the mold pushing follower 55 ahead of it until gates 72 and 73 are nolonger sealed. Thereafter, molding material is introduced into the moldvia gates 72 and 73 in the same manner as material was introduced intomold 10 via gates 26 and 27 in the description of the embodiment shownin FIG. 1. Thereafter, followers 56 and 57 are moved distally and gates74 and 77 are unsealed substantially as described above with respect tofollower 55 and gates 72 and 73.

Eventually, follower 57 reaches follower 58 and the followers 55 to 58proceed to transfer from drainage lumen wire 51 and inflation lumen wire52 to first and second receiving wires 53 and 54. This transfer issubstantially the same as the transfer of followers 32 and 33 from thefirst wire 31 to second wire 34 in the embodiment shown in FIG. 2described above.

After the followers 55 to 58 have been pushed to the distal end of mold50, the molding material is hardened, the mold opened, and the hollowarticle stripped from the wires as described above in connection withthe embodiments shown in FIGS. 1 and 2. Thereafter, at least onedrainage eye is provided toward the distal end of the catheter incommunication with the drainage lumen. Additionally, at least one eye isprovided in communication with the inflation lumen and a balloon isbonded to the catheter so that the inflation lumen is is incommunication with the space defined by the catheter shaft and theinside of the balloon.

For convenience of illustration, the followers 55 to 58 shown in FIG. 4are not interlocking. However, it is to be understood that the followersused in this embodiment are preferably the same type of interlockingfollowers shown in FIG. 3.

Referring now to FIG. 4A, there is shown a cross section of FIG. 4 alonglines 4A--4A. It will be observed from FIG. 4A that while inflationlumen wire 52 is cylindrical, drainage lumens wire 51 preferably is not.Rather, drainage lumen wire 51 is cylindrical with a small arcuatesection cut out. As is shown in FIG. 4A, inflation lumen wire 52desirably is fitted into the space provided by the arcuate cut indrainage lumen wire 51. Thus, inflation lumen wire 52 and drainage lumenwire 51 are accommodated in a relatively small cross sectional area, andat the same time the drainage lumen produced has a desirable relativelylarge cross sectional area. As shown in FIG. 4A, follower 56 desirablyhas a set of air vents 157 and 158 similar to those shown in FIG. 1A.

As was noted, supra in connection with the description of FIG. 1, therunners, lines and gates are preferably identically designed andsymmetrically arranged with respect to mold 50. The reason for this asnoted supra is that by employing such a design and arrangementdistortion of the wires in the mold is minimized. Such an effect isunexpected in the embodiment shown in FIG. 4A since inflation lumen wire52 is much closer to gate 75 than it is to gate 74, and further sinceinflation lumen wire 52 is shielded from gate 74 by drainage lumen wire51. It therefore might be expected that inflation lumen wire 52 would bedistorted toward drainage lumen wire 51 in response to the pressure ofmolding material injected through gate 75. To the contrary, however, wehave found that by using the arrangement of wires and gates shown inFIG. 4A, the inflation lumen wire remains stable.

While the reason why the arrangement of gates and wires shown in FIG. 4Aworks is not fully understood, it is known that when gates 74 to 77 arenot employed in the embodiment shown in FIG. 4, the small, e.g. 0.035inch diameter, inflation lumen wire 52 is distorted toward the insidewall of mold 50. This, of course, results in a useless Foley catheterwith holes in the inflation lumen. It therefore appears that thearrangement of gates and wires shown in FIG. 4A in part counteracts thetendency that the inflation lumen wire 52 would otherwise have todistort outwardly toward the inside wall of mold 50. It is also believedthat the lower molding pressures permitted by the use of the gates asdescribed above contributes to the stability of the wires.

In the embodiment shown in FIG. 4, there is provided three sets of gateswhich are initially sealed by three followers. However, a full lengthFoley catheter of the type described herein can be produced if one setof gates and its corresponding follower (preferably either gates 74 and75 and follower 56 or gates 76 and 77 and follower 57) is eliminated. Ofcourse, one set of gates but not its corresponding follower may beeliminated.

It is also to be understood that receiving wires 53 and 54 and follower58 may be eliminated in producing a Foley catheter according to thepresent invention. When receiving wires 53 and 54 are not used, however,molding material flows into the holes in followers 55 and 57 at thedistal end of the mold to provide a catheter with pigtails at its distalend. These pigtails must be removed, e.g. by cutting and polishing,before the catheter is inserted into the patient.

Additionally, it is to be understood that more than four followers maybe provided in the mold 50 to provide additional stability to the wiresprovided therein. And, each additional follower may or may not beprovided with a set of gates that are sealed by the follower at thebeginning of the molding process.

It should also be understood that the number of followers and gatesassociated therewith may be increased in similar fashion in theembodiments of the invention shown in FIGS. 1 and 2. The number offollowers used may be increased with followers, in which case it ispreferred to use a single continuous follower as shown in FIG. 5.

Referring to FIG. 5, there is shown an apparatus for producing a closedended hollow article, which for purposes of illustration may be anon-retention urinary catheter. As shown in FIG. 5, there is providedmold 100 with a first wire 101 provided therein. A second wire 102 isalso provided spaced from the distal end of the first wire 101 andlongitudinally aligned therewith. Wires 101 and 102 are attached to asuitable source which, as shown in FIG. 5, are the proximal and distalends of the mold 100, respectively. Toward the proximal end of the mold100, first wire 101 widens so that the proximal end of the catheterproduced is funnel shaped.

As noted, supra, the follower 103 spans a substantial portion, e.g. atleast 50% and preferably at least 75%, of the first wire 101. At thebeginning of the molding process, follower 103 is positioned as shown inFIG. 5. That is, the proximal end of follower 103 is located justdistally of input gates 105 and 106 and extends the remaining length offirst wire 101 to span the space between the first wire 101 and secondwire 102. Another set of gates 107 and 108 is also provided along thelength of the mold. Thus, the single follower 103 shown in FIG. 5performs the dual function of initially sealing gates 107 and 108 andbridging the gap between first wire 101 and second wire 102 to insurethe smooth transition of the proximal portion of follower 103 ontosecond wire 102.

To begin the process, molding material, e.g. catalyzed silicone rubber,is introduced into annular space 120 via line 109, runners 110 and 111,lines 112 and 113 and gates 105 and 106 at the proximal end of mold 100.The runners, lines and gates are again preferably, but not essentially,identically designed and symmetrically oriented with respect to mold100. The silicone rubber pushes follower 103 distally in the moldthereby unsealing gates 107 and 108. Thereafter, molding material isintroduced into the mold via gates 107 and 108 and follower 103continues to move distally in the mold. Eventually, follower 103 totallydisengages from the first wire 101 to entirely engage second wire 102and subsequently reaches the distal end of the mold 100. Thereafter thesilicone rubber is cured, the mold is opened, and the non-retentionurinary catheter is stripped from wire 101 as described above.

It will be understood by those skilled in the art that a followersimilar to the one shown in FIG. 5 can be used to produce a full lengthFoley catheter. In such case, a single continuous follower would be usedin place of followers 55, 56, 57 and 58 in FIG. 4.

It will be recalled that it was noted supra, that molding material maybe introduced into the mold through the proximal end of the mold.Further, it was noted supra that in appropriate circumstances moldingmaterial may be introduced into the mold through single gates instead ofthrough sets of gates along the length of the mold. Finally, it wasnoted supra that the source of molding material need not be the same foreach gate in the mold.

Referring now to FIG. 8 there is shown a mold 200 which incorporateseach of the features noted immediately above. As shown in FIG. 8, wire201 is hung from a source 202 and terminates at 203 close to the distalend 204 of the mold 200. As shown in FIG. 8, followers 205 and 206 fitinto annular space 207 in close abutment with wire 201 and the insidewall of mold 204.

At the start of the molding process, molding material is introduced intothe mold 200 from a source (not shown) through line 208 and gate 209.The molding material flows through annular space 207 pushing follower205 ahead of it until the distal end of follower 205 reaches theproximal end of follower 206. In the meantime molding material has beenintroduced from a source (not shown) into line 210 and gate 211.Injection of molding material into the mold through gate 211 isprevented up to this point however, since follower 206 is initiallypositioned in the mold 200, as shown in FIG. 8, to seal gate 211.However, after follower 205 reaches follower 206 both followers arepushed distally through the mold in response to the pressure of moldingmaterial injected through gate 209. Eventually, gate 211 is unsealedwhen the proximal end of follower 205 passes gate 211 and thereafter,molding material is injected into mold 200 through gate 211. Thereafterfollowers 205 and 206 are pushed to the distal end of the mold 200 andthe hollow article so produced is stripped from wire 201 as describedabove in connection with the other embodiments of the present invention.

With respect to all the embodiments described above, it will beappreciated that all the molding material in the mold will harden duringthe curing process. As a result, the hollow article stripped from thewire will have appendages corresponding to the shape of the gates,lines, etc. of the mold. To obtain a useful article, these appendagesmust be cut from the hollow article. The imperfections at the cut pointsmay then be polished. Alternatively, the hollow article may be dipped afew times into a dispersion of polymer material and hardened to coverthe imperfections on the surface of the molded hollow article.

As was noted supra, the clearances used in the present invention shouldbe maintained so that molding material will not flow either between thefollower and inside of the mold or between the follower and wires. Whenusing catalyzed silicone rubber, clearances of about 0.0015 inch havegiven good results although it is contemplated that clearances of up to0.002 inches or even 0.005 inches could be used. At these clearances,generally the followers will not move prematurely. However, variousdevices may be used to insure that the followers remain properlypositioned in the mold. For example, the followers, the wall of themold, or both, may be magnetized. Additionally, rectracting pinsactivated by mechanical means or by electrical solenoids may be used.Or, a vacuum may be applied through the walls of the mold. Finally, anuncured silicone rubber adhesive may be used to maintain the followersin the proper position in the mold.

While the present invention has been described with respect to certainpreferred embodiments, variations and equivalents may be perceived bythose skilled in the art while nevertheless not departing from the scopeof the invention as described by the claims appended hereto.

We claim:
 1. The process of manufacturing a hollow article whichcomprises:a. providing a mold with a first wire longitudinally disposedtherein and containing first and second followers disposed about thefirst wire in close abutment with both the first wire and inside wall ofthe mold, said followers maintaining the first wire spaced from theinside wall of the mold so as to define an annular space between thefirst wire and the inside wall of the mold; b. positioning the secondfollower proximally of the distal end of the mold and spaced distallyfrom the first follower thereby sealing a set of gates provided in themold; c. introducing a molding material under pressure into said annularspace proximally of the proximal end of the first follower therebydistally displacing the first follower; d. continuing the distaldisplacement of the first follower thereby engaging the second followerand, thereafter, distally displacing both the first and second followersthereby unsealing the set of gates; e. thereafter introducing moldingmaterial into the annular space through the set of gates to continue thedistal displacement of the followers while material is molded around thefirst wire; and f. stripping the resulting hollow article from the firstwire.
 2. The process of claim 1 which further comprises:a. providing atleast a third follower in close abutment with the first wire and insidewall of the mold; b. positioning the third follower proximally of thedistal end of the mold and spaced distally from the second follower; andc. continuing the distal displacement of the first and second followersuntil the third follower is engaged and thereafter distally displacingthe first, second and third followers.
 3. The process of claim 2 whereinthe distal displacement of the three followers unseals a second set ofgates, previously sealed by the third follower and, thereafter,introducing molding material into the annular space through the secondset of gates.
 4. The process of claim 1 which further comprises:a.providing a second wire spaced distally from the first wire andlongitudinally aligned therewith; b. bridging the space between thefirst and second wires with a third follower, said third followerpartially engaged with the first and second wires; and c. continuing thedistal displacement of the first and second followers until the thirdfollower is engaged and, thereafter, distally displacing the threefollowers off the first wire and onto the second wire whereby there isformed a hollow article with a solid tip.
 5. The process ofmanufacturing a hollow article with a solid tip which comprises:a.providing a mold with a first wire longitudinally disposed therein andcontaining a first follower disposed about the first wire in closeabutment with both the first wire and the inside wall of the mold, saidfirst follower maintaining the first wire spaced from the inside wall ofthe mold so as to define an annular space between the first wire and theinside of the mold; b. providing a second wire spaced distally from thefirst wire and longitudinally aligned therewith; c. bridging the spacebetween the first wire and the second wire with a second follower; d.introducing a molding material into said annular space proximally of theproximal end of the first follower thereby distally displacing the firstfollower; e. continuing to introduce said molding material into the moldto continue the distal displacement of the first follower, therebyengaging the second follower and, thereafter, distally displacing thefirst and second follower off the first wire and into the second wirewhereby there is formed the tip of the hollow article; and f. strippingthe resulting hollow article from the first wire.
 6. The process ofmanufacturing a hollow article which comprises:a. providing a mold witha first wire longitudinally disposed therein and containing a followerdisposed about the first wire in close abutment with both the first wireand inside wall of the mold, said follower maintaining the first wirespaced from the inside wall of the mold so as to define an annular spacebetween the first wire and the inside of the mold; b. providing a secondwire spaced distally from said first wire and longitudinally alignedtherewith; c. positioning the first follower in the mold so that itspans at least 50% of the length of the first wire and at the same timebridges the space between the first wire and second wire; d. introducinga molding material into said annular space proximally of the proximalend of the follower under a pressure sufficient to distally displacesaid follower; e. continuing to introduce said molding material intosaid annular space until said follower is entirely displaced off saidfirst wire and onto said second wire whereby there is formed a hollowarticle having a solid tip; and f. stripping the resulting hollowarticle from said first wire.
 7. The process of claim 6 which furthercomprises:a. sealing a set of gates in the mold by positioning thefollower as in step (c) above; b. distally displacing the proximal endof the follower past the set of gates to unseal the set of gates; and c.thereafter introducing molding material into the annular space throughthe set of gates and continuing to distally displace the follower whilematerial is molded around the first wire.
 8. The process ofmanufacturing a hollow article which comprises:a. providing a mold witha first wire longitudinally disposed therein and containing a followerdisposed about the first wire in close abutment with both the first wireand inside wall of the mold, said follower maintaining the first wirespaced from the inside wall of the mold so as to define an annular spacebetween the first wire and inside of the mold; b. positioning thefollower so that it seals a set of gates provided in the mold and spansat least about 50% of the length of the first wire; c. introducing amolding material into said annular space proximally of the proximal endof the follower under pressure thereby distally displacing the firstfollower past the set of gates; d. thereafter introducing the moldingmaterial into the annular space through the set of gates and continuingto distally displace the follower while material is molded around thefirst wire; and e. stripping the resulting hollow article from the firstwire.
 9. A process for producing a hollow article with a tip whichcomprises:a. providing a mold with a drainage lumen wire longitudinallydisposed therein, said drainage lumen wire having a widened crosssection at its proximal end; b. providing an inflation lumen wirelongitudinally disposed in the mold, said inflation lumen wire alsohaving a widened cross section at its proximal end; c. positioning afirst follower distally of the widened portions of the drainage lumenand inflation lumen wires, said first follower sealing a first set ofgates in the mold; d. positioning a second follower distally of saidfirst follower, said second follower sealing a second set of gates inthe mold, said first and second followers disposed about the drainagelumen and inflation lumen wires in close abutment with the drainagelumen and inflation lumen wires and inside wall of the mold, said firstand second followers maintaining the drainage lumen and inflation lumenwires and inside wall of the mold spaced from each other so as to definea molding channel in the mold; e. introducing molding material underpressure into the molding channel proximally of the proximal end of thefirst follower whereby material is molded around the widened portions ofthe drainage lumen and inflation lumen wires; f. continuing introducingmolding material into the molding channel thereby distally displacingthe first follower and unsealing the first set of gates; g. thereafterintroducing molding material into the molding channel through the firstset of gates and continuing to distally displace the first followerwhile molding material is molded around the drainage lumen and inflationlumen wires; h. continuing the distal displacement of the first followerthereby also distally displacing the second follower and unsealing thesecond set of gates; i. thereafter introducing material into the moldingchannel through the second set of gates and continuing to distallydisplace the first and second followers while material is molded aroundthe drainage lumen and inflation lumen wires; j. continuing the distaldisplacement of the first and second followers until both followers havebeen distally displaced from the inflation lumen and drainage lumenwires, thereby forming a hollow article with a solid tip; k. strippingthe resulting hollow article from the drainage and inflation lumenwires.
 10. A process for producing a hollow article with a tip accordingto claim 9 which further comprises:a. providing a third follower inclose abutment with the drainage lumen and inflation lumen wires andinside wall of the mold; b. positioning the third follower distally ofthe second follower, said third follower sealing a third set of gates inthe mold; c. continuing the distal displacement of the first and secondfollowers thereby also distally displacing the third follower andunsealing the third set of gates; d. thereafter introducing materialinto the molding channel through the third set of gates and continuingto distally displace the first, second and third followers whilematerial is molded around the drainage lumen and inflation lumen wires.11. A process for producing a hollow article with a solid tip accordingto claim 10 which further comprises:a. providing a first receiving wirespaced distally from the drainage lumen wire and longitudinally alignedtherewith; b. providing a second receiving wire spaced distally from theinflation lumen wire and longitudinally aligned therewith; c. bridgingthe space between the drainage lumen and inflation lumen wires and firstand second receiving wires with a fourth follower, said fourth followerpartially engaged with the drainage lumen and inflation lumen wires andthe first and second receiving wires; d. continuing the distaldisplacement of the first, second and third followers until the fourthfollower is engaged and thereafter distally displacing the fourfollowers off the drainage lumen and inflation lumen wires and onto thefirst and second receiving wires whereby there is formed a hollowarticle with a solid tip.
 12. A process for producing a hollow articleaccording to claim 9 which further comprises:a. providing a firstreceiving wire spaced distally from the drainage lumen wires andlongitudinally aligned therewith; b. providing a second receiving wirespaced distally from the inflation lumen wire and longitudinally alignedtherewith; c. bridging the space between the drainage lumen andinflation lumen wires and first and second receiving wires with a thirdfollower, said third follower partially engaged with the drainage lumenand inflation lumen wires and and first and second receiving wires; d.continuing the distal displacement of the first and second followersuntil the third follower is engaged and thereafter distally displacingthe three followers off the drainage lumen and inflation lumen wires andonto the first and second receiving wires whereby there is formed ahollow article with a solid tip.
 13. The process of manufacturing ahollow article which comprises:a. providing a mold with a first wirelongitudinally disposed therein and containing first and secondfollowers disposed about the first wire in close abutment with both thefirst wire and inside wall of the mold, said followers maintaining thefirst wire spaced from the inside wall of the mold so as to define anannular space between the first wire and the inside wall of the mold; b.positioning the second follower proximally of the distal end of the moldand spaced distally from the first follower thereby sealing a gateprovided in the mold; c. introducing a molding material under pressureinto said annular space proximally of the proximal end of the firstfollower thereby distally displacing the first follower; d. continuingthe distal displacement of the first follower thereby engaging thesecond follower and, thereafter, distally displacing both the first andsecond followers thereby unsealing the gate; e. thereafter introducingmolding material into the annular space through the gate to continue thedistal displacement of the followers while material is molded around thefirst wire; and f. stripping the resulting hollow article from the firstwire.
 14. The process of manufacturing a hollow article whichcomprises:a. providing a mold with a first wire longitudinally disposedtherein and containing a follower disposed about the first wire in closeabutment with both the first wire and inside wall of the mold, saidfollower maintaining the first wire spaced from the inside wall of themold so as to define an annular space between the first wire and insideof the mold; b. positioning the follower so that it seals a gate,provided in the mold and spans at least about 50% of the length of thefirst wire; c. introducing a molding material into said annular spaceproximally of the proximal side of the follower under pressure therebydistally displacing the first follower past the gate; d. thereafterintroducing the molding material into the annular space through the gateand continuing to distally displace the follower while material ismolded around the first wire; and f. stripping the resulting hollowarticle from the first wire.